p53/Glut9调控肝细胞尿酸转运及高尿酸诱导NAFLD发病的作用及其分子机制

Nonalcoholic fatty liver disease (NAFLD) is one of the chronic liver diseases with high morbility, but its pathogenesis is poorly understood. Recent studies found that the glucose transporter Glut9 is a uric acid transport in hepatocytes and its expression was regulated by p53. Our previous studies revealed that the p53 expression level in the hepatocytes from NAFLD mouse model was increased and inhibition of p53 expression could decrease the hepatic steatosis, high serum uric acid was significantly associated with pathogenesis of NAFLD and the decreased uric acid level could attenuate the pathological changes of NAFLD. However, the pathogenic mechanism of p53/Glut9-regulated and uric acid-induced pathogenesis of NAFLD remains unknown. In this research project, by using laser confocal microscopy, flow cytometry, target gene overexpression and siRNA-dependent silence or knockout as well as high uric acid or NAFLD cell models and hyperuricemia or NAFLD mouse models, we try to research and determine the roles and mechanisms the p53 up-regulating Glut9 expression to promote the uric acid transport into the cells, high level uric acid up-regulating the expression of ChREBP, a carbohydrate-responsive element-binding protein, and activating the SREBPs, the transcription factors for regulation of fatty synthetic enzymes, and evoking the NLRP3 inflammosome, endoplasmic reticulum stress (ERS) and mitochondrial oxidative stress (MOS) by ROS production through NADP/NADPH oxidase and lysosome pathways, which involved in the pathogenesis of NAFLD. The findings of this project will possess high originality and clinical significance.

非酒精性脂肪性肝病（NAFLD）是高发慢性肝病，其发病机制未完全明了。近年报道Glut9是肝细胞尿酸转运体且其表达受p53调控。我们前期研究发现NAFLD小鼠肝细胞p53表达水平增高、抑制p53可减少细胞脂变，高血清尿酸与NAFLD发病密切相关、降低尿酸可减轻NAFLD病变程度，但机制不明。本项目拟采用激光共聚焦显微镜、流式细胞术、靶基因过表达与siRNA沉默或敲除等技术以及高尿酸和NAFLD细胞模型、高尿酸血症和NAFLD小鼠模型，探讨并确定p53上调Glut9表达促进尿酸转运入胞、高水平尿酸上调脂质合成相关糖类应答元件结合蛋白ChREBP表达及激活调控脂质合成酶类表达的转录因子SREBPs、经NADP/NADPH氧化酶或溶酶体途径产生ROS激活NLRP3炎症小体并引发内质网应激（ERS）和线粒体氧化应激反应（MOS），从而参与NAFLD发病的作用及分子机制，具有较高创新性及临床意义。

非酒精性脂肪性肝病（Nonalcoholic Fatty Liver Disease，NAFLD）是临床上非常常见的一种慢性肝病，近年来随着国人生活水平的快速提高，该疾病在中国的发病率也处于快速上升期。直到目前临床上并无针对性治疗NAFLD的药物，很重要的原因就是其发病机制目前仍未完全明确。因此，探究NAFLD发病机制对治疗该疾病具有非常重要的意义。最近，肿瘤抑制因子p53在代谢性疾病当中的作用越来越受到关注，本研究首先在小鼠及体外细胞模型上进行试验，发现功能性p53的沉默能够显著改善NAFLD造模所致小鼠肝脏及体外细胞内的甘油三酯和脂质累积。继而发现p53的沉默对肝细胞的自噬有诱导作用，并可以引发自噬调控蛋白HMGB1的胞核-胞浆转位。肝细胞内的自噬体与脂质具有共定位现象，同时在体外肝细胞进行自噬诱导或阻滞，分别可以促进或抑制胞内脂质降解。最后在体外细胞模型证明了p53沉默对抗NAFLD的作用是通过HMGB1介导的自噬途径发挥。本研究阐明了肿瘤抑制因子p53在代谢性疾病当中具有的重要作用，并且这种作用与对自噬的调控密切相关。p53-自噬途径可能是NAFLD治疗的潜在靶点。